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首页> 外文OA文献 >Multispectral VNIR Observations by the Opportunity Rover Pancam of Multiple Episodes of Aqueous Alteration in Marathon Valley, Endeavour Crater, Mars
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Multispectral VNIR Observations by the Opportunity Rover Pancam of Multiple Episodes of Aqueous Alteration in Marathon Valley, Endeavour Crater, Mars

机译：火星“奋进”陨石坑马拉松山谷水蚀多发的机会漫游者全景摄影的多光谱VNIR观测

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Since early 2015, the Mars Exploration Rover Opportunity has been exploring the break in the rim of Endeavour Crater dubbed Marathon Valley by the rover team. Marathon Valley was identified by orbital hyperspectral data from the MRO CRISM as having a relatively strong spectral feature in the 2.3 micrometer region indicative of an Mg or Fe-OH combination overtone absorption band indicative of smectite clay. Earlier in its mission, Opportunity examined the Matijevic Hill region on the more northerly Cape York crater rim segment and found evidence for smectite clays in a stratigraphically lower, pre-impact formed unit dubbed the Matijevic formation. However, the smectite exposures in Marathon Valley appear to be associated with the stratigraphically higher Shoemaker formation impact breccia. Evidence for alteration in this unit in Marathon Valley is provided by Pancam multispectral observations in the 430 to 1010 nm visible/near infrared (VNIR) spectral range. Sinuous troughs ("red zones") contain fragmented cobbles and pebbles displaying higher blue-to-red slopes, moderately higher 535 nm band depths, elevated 754 to 934 nm, and negative 934 to 1009 nm slopes. The lack of an absorption at 864 to 904 nm indicates the lack of crystalline red hematite in these red zones, but likely an enrichment in nanophase ferric oxides. The negative 934 to 1009 nm slope is potentially indicative of the presence of adsorbed or structurally bound water. A scuff in a red zone near the southern wall of Marathon Valley uncovered light-toned soils and a pebble with an 803 to 864 nm absorption resembling that of light-toned Fe-sulfate bearing soils uncovered by the Spirit rover in the Columbia Hills of Gusev crater. APXS chemical measurements indicated enrichments of Mg and S in the scuff soils and the pebble, Joseph Field, with the strongest 803 nm band- consistent with Mg and Fe sulfates. The presence of Fe and Mg sulfates can be interpreted as evidence of a potentially later episode of aqueous alteration with an earlier, neutral to alkaline pH episode forming the Fe/Mg smectites and a later acid pH episode forming the Fe and Mg sulfates.
机译：自2015年初以来，“火星探索漫游者号”就一直在探索由漫游者队命名为“马拉松山谷”的“奋进号”陨石坑的边缘。根据MRO CRISM的轨道高光谱数据确定的马拉松谷在2.3微米区域具有相对较强的光谱特征，表明存在蒙脱石粘土的Mg或Fe-OH组合物泛音吸收带。在执行任务的早期，Opportunity检查了更北的约克角火山口边缘部分的马蒂耶维奇山地区，并发现了地层较低，受撞击前形成的被称为马蒂耶维奇地层的蒙脱石粘土的证据。但是，马拉松山谷中蒙脱石的暴露似乎与地层较高的鞋匠地层冲击角砾岩有关。 Pancam在430至1010 nm可见/近红外（VNIR）光谱范围内的多光谱观测提供了马拉松山谷中该单元发生变化的证据。蜿蜒的低谷（“红色区域”）包含碎片化的鹅卵石和卵石，它们具有较高的蓝到红斜率，中等较高的535 nm波段深度，754至934 nm的升高斜率和934至1009 nm的负斜率。在864至904 nm处缺乏吸收表明在这些红色区域中缺乏结晶红色赤铁矿，但可能是纳米相三氧化二铁的富集。负934至1009 nm的斜率可能表示存在吸附或结构结合的水。马拉松河谷南壁附近的红色区域中的一块磨损发现了浅色土壤，而卵石的吸收强度为803至864 nm，类似于被Gusev哥伦比亚山的精神漫游者发现的浅色调含硫酸铁的土壤火山口。 APXS的化学测量结果表明，磨损的土壤和卵石（约瑟夫菲尔德）中的Mg和S富集，最强的803 nm带与Mg和Fe硫酸盐一致。 Fe和Mg硫酸盐的存在可以解释为水蚀发生的潜在后期证据，较早的中性至碱性pH值形成Fe / Mg蒙脱石，而酸性pH值后期形成Fe和Mg硫酸盐。

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